1. Field of the Invention
The present invention relates to a substrate processing apparatus and substrate processing method for performing a predetermined liquid process, such as a cleaning process, on a substrate, such as a semiconductor wafer. The present invention further relates to a storage medium that stores a program for executing the method.
2. Description of the Related Art
In the process of manufacturing semiconductor devices, liquid processes are frequently used, in which a process liquid is supplied onto a target substrate, such as a semiconductor wafer or glass substrate. For example, a process of this kind is a cleaning process for removing particles and/or contaminants deposited on a substrate.
As a substrate processing apparatus used for this purpose, there is known an apparatus that performs a cleaning process on a substrate, such as a semiconductor wafer, held on a spin chuck, in which a process liquid, such as a chemical liquid, is supplied onto the substrate, while the substrate is rotated. In general, according to apparatuses of this kind, a process liquid is supplied onto the center of a substrate, and the substrate is rotated to spread the process liquid outward, thereby forming a liquid film and throwing off the process liquid out of the substrate. After the cleaning process, a rinsing process is performed, such that a rinsing liquid, such as purified water, is supplied onto the substrate, while the substrate is rotated at a speed higher than the chemical liquid process, thereby forming a liquid film of the rinsing liquid and throwing off the rinsing liquid out of the substrate. In light of this, there proposed a structure in which a drain cup is disposed to surround a substrate and to receive and discharge a process liquid or rinsing liquid thrown off outward from the substrate (for example, Jpn. Pat. Appln. KOKAI Publication No. 2002-368066).
According to this substrate processing apparatus, an alkaline chemical liquid and/or an acidic chemical liquid are used as chemical liquids. Since these chemical liquids are relatively expensive, there is proposed a technique for collecting and reusing them by circulation (for example, Jpn. Pat. Appln. KOKAI Publication No. 5-243202). In order not to collect a chemical liquid thinned down by mixture of purified water after water washing used as a rinsing process, this publication discloses a method for selectively using a plurality of cups. For the same purpose, this publication further discloses a technique in which a chemical liquid is first discharged to a drain line for several seconds in the initial stage of a chemical liquid process after a water washing process, and then the line is switched to a collection line to collect the chemical liquid.
In the case of the former technique disclosed in Publication No. 5-243202, the apparatus needs to have a larger size with a complex structure. In the case of the latter technique disclosed in Publication No. 5-243202, a rinsing process needs to be performed by use of a higher rotational speed than that used in the chemical liquid process for the sake of a reliable rinsing effect, and causes purified water used as a rinsing liquid to be left at an upper side of a cup. In this case, it takes a longer time to wash away the purified water, thereby increasing the amount of chemical liquid discharged to the drain line, and decreasing the collection rate of the chemical liquid.